# transformcalc¶

## Synopsis¶

Perform calculations on linear transformation matrices

## Usage¶

```transformcalc [ options ]  inputs [ inputs ... ] operation output
```
• inputs: the inputs for the specified operation
• operation: the operation to perform, one of: invert, half, rigid, header, average, interpolate, decompose, align_vertices_rigid (see description section for details).
• output: the output transformation matrix.

## Description¶

invert: invert the input transformation:

matrix_in invert output

half: calculate the matrix square root of the input transformation:

matrix_in half output

rigid: calculate the rigid transformation of the affine input transformation:

matrix_in rigid output

header: calculate the transformation matrix from an original image and an image with modified header:

mov mapmovhdr header output

average: calculate the average affine matrix of all input matrices:

input … average output

interpolate: create interpolated transformation matrix between input (t=0) and input2 (t=1). Based on matrix decomposition with linear interpolation of translation, rotation and stretch described in Shoemake, K., Hill, M., & Duff, T. (1992). Matrix Animation and Polar Decomposition. Matrix, 92, 258-264. doi:10.1.1.56.1336:

input input2 interpolate output

decompose: decompose transformation matrix M into translation, rotation and stretch and shear (M = T * R * S). The output is a key-value text file containing: scaling: vector of 3 scaling factors in x, y, z direction; shear: list of shear factors for xy, xz, yz axes; angles: list of Euler angles about static x, y, z axes in radians in the range [0:pi]x[-pi:pi]x[-pi:pi]; angle_axis: angle in radians and rotation axis; translation : translation vector along x, y, z axes in mm; R: composed roation matrix (R = rot_x * rot_y * rot_z); S: composed scaling and shear matrix:

matrix_in decompose output

align_vertices_rigid: align two sets of landmarks using a rigid transformation. Vertex coordinates are in scanner space, corresponding vertices must be stored in the same row of moving.txt and fixed.txt. Requires 3 or more vertices in each file. Algorithm: Kabsch ‘A solution for the best rotation to relate two sets of vectors’ DOI:10.1107/S0567739476001873:

input moving.txt fixed.txt align_vertices_rigid output

## Options¶

### Standard options¶

• -info display information messages.
• -quiet do not display information messages or progress status. Alternatively, this can be achieved by setting the MRTRIX_QUIET environment variable to a non-empty string.
• -debug display debugging messages.
• -force force overwrite of output files. Caution: Using the same file as input and output might cause unexpected behaviour.
• -nthreads number use this number of threads in multi-threaded applications (set to 0 to disable multi-threading).
• -help display this information page and exit.
• -version display version information and exit.

Author: Max Pietsch (maximilian.pietsch@kcl.ac.uk)

Copyright: Copyright (c) 2008-2018 the MRtrix3 contributors.

This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, you can obtain one at http://mozilla.org/MPL/2.0/

MRtrix3 is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

For more details, see http://www.mrtrix.org/